Ice protection of aircraft leading edge structures has traditionally been provided on large commercial aircraft through the use of bleed air. Smaller aircraft have used combinations of inflatable rubber de-icing boots, and de-icing fluid. Helicopters have had significant experience of electrical ice protection solutions. Most previous applications of helicopter electrical ice protection have been on fixed structures, which by definition do not move. The only exception to this being electrical ice protection on helicopter rotor blades where the power is transmitted through a slip ring system of joints, the technology of which is used over much of the engineering industry.
There is now a move to incorporate electrical de-icing systems into commercial fixed wing aircraft. The areas of commercial fixed wing aircraft that have particular need for ice protection are the movable leading edge slat structures.
Electrical power is transferred for other reasons across mechanically actuated joints. This is traditionally achieved in a variety of ways. For example, a folding arm type joint may have an electrical cable within each arm connected by a slip ring type rotary joint between the arms, which rotates as the arms are extended. A telescopic tube may have a helically wound electrical cable therein, similar to a telephone cable, the effective length of which changes with telescoping of the tube. An electrical cable may alternatively be encased by chain links, which limit the bend radius of the cable as the ends of the chain links are moved towards and away from one another.
The current technological options suffer various disadvantages of being heavy, having a high space requirement, causing fretting of an electrical cable, or excessive manipulation of an electrical cable which can cause electrical wires of the cable to break, leading to reliability issues.
WO2006/027624A describes a coupling arrangement for coupling services between an aircraft wing fixed aerofoil component and a extendable leading edge slat mounted thereto. The coupling arrangement includes a housing for connection to the fixed aerofoil structure, and a hollow telescopic assembly extendable between a retracted and an extended position. A service carrying conduit arrangement carries the services, such as electrical power cables, between the fixed aerofoil component and the leading edge slat, and extends through the hollow telescopic assembly. The service carrying conduit arrangement is flexible and excess thereof is located within the housing when the telescopic assembly is in the retracted position. The excess weight and space requirements of the housing for storing the excess of the flexible conduit, together with the manipulation of the electrical cables within the conduit when stored in the housing, exemplifies some of the problems with prior art solutions.
There is therefore a need in the art for an improved system for electrically connecting structures movable relative to one another.